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| United States Patent |
6,075,472
|
|
Goode, III
, et al.
|
June 13, 2000
|
Synchro-to-digital conversion with windowed peak determination
Abstract
The present invention is directed to a method and apparatus which utilizes
a software-based digital signal processing circuit to generate a signal
which is representative of the status of a movable component. A preferred
embodiment of the apparatus of the present invention includes a synchro
which is connected to a movable component. An analog reference excitation
may be applied to the synchro, and the synchro generates analog synchro
signals which bear a relationship to the status of the movable component.
The analog synchro signals are converted to digital synchro signals by a
plurality of analog-to-digital converters. A digital reference signal and
the digital synchro signals are provided to a software-based digital
signal processing circuit which preferably corrects constant and
time-varying errors in the digital synchro signals and generates a status
signal which is representative of the status of the movable component. For
instance, the status signal may represent the angular position of the
movable component. A different embodiment of the status signal may
represent the angular velocity of the movable component.
| Inventors:
|
Goode, III; Joseph W. (Alpharetta, GA);
Smith; John R. (Buford, GA);
Ashcraft; Kenneth D. (Alpharetta, GA)
|
| Assignee:
|
Universal Avionics Systems Corporation--Instrument Division (Norcross, GA);
L-3 Communications Corporation (New York, NY)
|
| Appl. No.:
|
227456 |
| Filed:
|
January 8, 1999 |
| Current U.S. Class: |
341/111; 318/652; 341/116; 702/145 |
| Intern'l Class: |
H03M 001/48 |
| Field of Search: |
341/111,116
318/652-661
702/145,150,151
|
References Cited
U.S. Patent Documents
| 3618073 | Nov., 1971 | Domchick et al. | 340/347.
|
| 4651130 | Mar., 1987 | Pennell | 341/116.
|
| 4876655 | Oct., 1989 | Carlton et al. | 364/487.
|
| 5034743 | Jul., 1991 | Deppe et al. | 341/116.
|
| 5646496 | Jul., 1997 | Woodland et al. | 341/116.
|
| 5757560 | May., 1998 | Fisherman | 359/821.
|
Other References
Synchro/Resolver Conversion Handbook Fourth Edition, DDC ILC Data Device
Corporation, 1974, pp. 1-342.
|
Primary Examiner: Williams; Howard L.
Attorney, Agent or Firm: Standley & Gilcrest LLP
Parent Case Text
This application claims the benefit of U.S. Provisional Application No.
60/072,377, filed Jan. 9, 1998.
Claims
What is claimed is:
1. A method for generating a status signal which is representative of the
status of a movable component, said method comprising:
providing digital synchro signals to a software-based digital signal
processing circuit;
determining two peak encompassing points of each digital synchro signal;
determining the peak amplitude of each digital synchro signal using a
respective two peak encompassing points; and
determining said status signal using at least one of the peak amplitudes.
2. The method of claim 1 further comprising filtering said digital synchro
signals prior to determining said status signal.
3. The method of claim 2 wherein said software-based digital signal
processing circuit bandpass filters said digital synchro signals.
4. The method of claim 1 further comprising:
providing a digital reference signal to said software-based digital signal
processing circuit;
sampling said digital reference signal;
determining two peak encompassing points of said digital reference signal;
and
determining a sample time of said two peak encompassing points of said
digital reference signal;
wherein the two peak encompassing points of each digital synchro signal are
determined using said sample time.
5. The method of claim 1 wherein determining said status signal further
includes factoring out attenuation of said digital synchro signals using
said software-based digital signal processing circuit.
6. The method of claim 5 wherein attenuation of said digital synchro
signals is factored out by:
comparing the peak amplitudes of said digital synchro signals in order to
determine the two highest peak amplitudes; and
determining said status signal using the two highest peak amplitudes of
said digital synchro signals.
7. The method of claim 1 wherein said status signal represents the angular
position of said movable component.
8. The method of claim 1 wherein said status signal represents the angular
velocity of said movable component.
9. A method for generating a status signal which is representative of the
status of a movable component, said method comprising:
generating analog synchro signals which bear a relationship the status of
said movable component;
converting said analog synchro signals to digital synchro signals;
generating a digital reference signal;
providing said digital synchro signals and said digital reference signal to
a software-based digital signal processing circuit; and
determining said status signal using said software-based digital signal
processing circuit, wherein determining said status signal includes:
sampling said digital reference signal, determining two peak encompassing
points of said digital reference signal, determining a sample time of said
two peak encompassing points of said digital reference signal, determining
the peak amplitude of each digital synchro signal using said sample time,
and determining said status signal using the peak amplitudes of said
digital synchro signals.
10. The method of claim 9 wherein determining the peak amplitude of each
digital synchro signal using said sample time includes:
determining two peak encompassing points of each digital synchro signal;
and
determining the peak amplitude of each digital synchro signal using said
two peak encompassing points of each digital synchro signal.
11. A method for generating a status signal which is representative of the
status of a movable component, said method comprising:
generating analog synchro signals which bear a relationship the status of
said movable component;
converting said analog synchro signals to digital synchro signals;
generating a digital reference signal;
providing said digital synchro signals and said digital reference signal to
a software-based digital signal processing circuit; and
determining said status signal using said software-based digital signal
processing circuit, wherein determining said status signal includes:
determining the peak amplitude of each digital synchro signal, and
determining said status signal using the peak amplitudes of said digital
synchro signals including factoring out attenuation of said digital
synchro signals;
wherein attenuation of said digital synchro signals is factored out by:
comparing the peak amplitudes of said digital synchro signals in order to
determine the two highest peak amplitudes; and determining said status
signal using the two highest peak amplitudes of said digital synchro
signals.
12. A method for generating a status signal which is representative of the
status of a movable component, said method comprising:
generating analog synchro signals which bear a relationship to the status
of said movable component;
converting said analog synchro signals to digital synchro signals;
generating a digital reference signal;
providing said digital synchro signals and said digital reference signal to
a software-based digital signal processing circuit; and
using said software-based digital signal processing circuit to:
filter said digital synchro signals and said digital reference signal;
sample said digital reference signal;
determine two peak encompassing points of said digital reference signal;
determine a sample time of said two peak encompassing points of said
digital reference signal;
determine the peak amplitude of each digital synchro signal using said
sample time;
compare the peak amplitudes of said digital synchro signals in order to
determine the two highest peak amplitudes; and
determine said status signal using the two highest peak amplitudes of said
digital synchro signals.
13. The method of claim 12 wherein said software-based digital signal
processing circuit bandpass filters said digital synchro signals and said
digital reference signal.
14. The method of claim 12 wherein determining the peak amplitude of each
digital synchro signal using said sample time includes:
determining two peak encompassing points of each digital synchro signal;
and
determining the peak amplitude of each digital synchro signal using said
two peak encompassing points of each digital synchro signal.
15. The method of claim 12 wherein said status signal represents the
angular position of said movable component.
16. The method of claim 12 wherein said status signal represents the
angular velocity of said movable output component.
17. An apparatus for generating a status signal which is representative of
the status of a movable component, said apparatus comprising:
a synchro connected to said movable component, said synchro adapted to
generate analog synchro signals which bear a relationship to the status of
said movable component;
at least one analog-to-digital converter in electrical communication with
said synchro, said at least one analog-to-digital converter for converting
said analog synchro signals to digital synchro signals; and
a software-based digital signal processing circuit in electrical
communication with said at least one analog-to-digital converter, said
software-based digital signal processing circuit adapted to determine two
peak encompassing points of each digital synchro signal, determine the
peak amplitude of each digital synchro signal using a respective two peak
encompassing points, and determine said status signal using at least one
of the peak amplitudes.
18. The apparatus of claim 17 wherein said software-based digital signal
processing circuit is comprised of a microprocessor.
19. The apparatus of claim 17 wherein said movable component is a rotatable
shaft.
20. The apparatus of claim 17 wherein said movable component is a rotor of
a motor.
21. The apparatus of claim 17 wherein said status signal represents the
angular position of said movable component.
22. The apparatus of claim 17 wherein said status signal represents the
angular velocity of said movable component.
23. The apparatus of claim 17 wherein said software-based digital signal
processing circuit is further adapted to factor out attenuation of the
peak amplitudes of said digital synchro signals prior to generating said
status signal.
24. A servomechanism comprising:
a motor having a stator and a rotor, said rotor driven to rotate about an
axis relative to said stator;
a synchro connected to said motor, said synchro adapted to generate analog
synchro signals which bear a relationship the status of said rotor;
at least one analog-to-digital converter in electrical communication with
said synchro, said at least one analog-to-digital converter adapted to
convert said analog synchro signals to digital synchro signals; and
a software-based digital signal processing circuit in electrical
communication with said at least one analog-to-digital converter, said
software-based digital signal processing circuit adapted to determine two
peak encompassing points of each digital synchro signal, determine the
peak amplitude of each digital synchro signal using a respective two peak
encompassing points, and determine said status signal using at least one
of the peak amplitudes.
25. The servomechanism of claim 24 wherein said software-based digital
signal processing circuit is comprised of a microprocessor.
26. The servomechanism of claim 24 wherein said status signal represents
the angular position of said rotor.
27. The servomechanism of claim 24 wherein said status signal represents
the angular velocity of said rotor.
28. The servomechanism of claim 24 wherein said software-based digital
signal processing circuit is further adapted to factor out attenuation of
the peak amplitudes of said digital synchro signals prior to generating
said status signal.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates generally to a method and apparatus for
converting analog synchro signals to a signal which is representative of
the status of a movable component, and more particularly, to a method and
apparatus which uses a software-based digital signal processing circuit to
generate a signal which is representative of the status of a movable
component. The present invention is particularly effective in a
servomechanism. A servomechanism is a system in which an input command
controls a physical output. A servomechanism may be comprised of a
mechanical output component which is moved in response to an electrical
input command. The mechanical output component may be a shaft which is
rotated about an axis in accordance with the electrical input command. For
example, a common electrical motor has a rotor which is driven by an
electrical input command to rotate about a stationary stator. In such
servomechanisms, the electrical input command can function to rotate the
shaft at a desired rotational velocity, to drive the rotor to a desired
rotational position, or to apply a desired torque or tension to a load.
A servomechanism commonly includes a closed feedback loop. A closed
feedback loop may compare the present electrical input command to a signal
which is representative of the present status of the mechanical output
component. If a variance exists between the two signals, an error signal
is generated which tends to eliminate the discrepancy between the present
status of the mechanical output component and the present electrical input
command.
In applications which utilize servomechanisms, it is often necessary to
know the precise status of the mechanical output component at any given
point in time. The closed feedback loop described above tends to eliminate
the variance between the present status of the mechanical output component
and the present electrical input command. As a result, such a closed
feedback loop provides a means to know the precise status of the
mechanical output component.
Knowledge of the precise status of the mechanical output component can be
used to improve the performance of the servomechanism. For example, the
performance of a common electrical motor can be improved if the rotational
velocity or position of the rotor is known. As mentioned above, a status
signal may represent the present status of the mechanical output
component. More precisely, a status signal may be an analog or digital
electrical signal which is indicative of the mechanical output component
relative to a predetermined starting or reference position. For example, a
status signal may represent a position between 0 and 360 degrees, wherein
0 degrees is defined as the starting or reference position of the
mechanical output component. For another example, a status signal may
represent the angular velocity of the mechanical output component. For yet
another example, a status signal may represent the torque of the
mechanical output component. In conjunction with a closed feedback loop, a
status signal can be used to improve the accuracy of the rotational
velocity, position, or torque of a mechanical output component. In like
manner, a status signal can be utilized to reduce undesirable torque
ripple and improve the efficiency of an electrical motor by controlling
the timing of the energizations and deenergizations of the windings of an
electrical motor.
A synchro is one well-known device for generating electrical signals which
bear a relationship to the status of a movable component. A synchro
control transmitter is an example of a synchro. A synchro control
transmitter accepts an analog reference excitation at its rotor terminals
and produces a three-wire set of analog synchro signals at its stator
terminals. The three-wire set of analog synchro signals is at the
reference frequency. The amplitude ratios of the line-to-line voltages of
the three-wire set of analog synchro signals are mathematically related to
the angular position of a movable component relative to a reference
position. As a result, the amplitude ratios of the line-to-line voltages
of the three-wire set of analog synchro signals may be utilized by avionic
instrumentation display units to determine the attitude or pitch of an
aircraft.
In addition to the synchro control transmitter, a number of different
synchro and resolver components can perform the same general function. In
particular, synchro control transformers, control differential
transmitters, transolvers, and Scott-T transformers may be utilized to
generate electrical signals which bear a relationship to the rotational
position of a rotor shaft. Similarly, transducers such as potentiometers,
brush encoders, optical encoders, and RVDTs/LVDTs may also be employed to
achieve the same general result.
The analog output signals from such components may be used to control the
operation of a servomechanism. In addition, the analog output signals from
such components may be converted to digital signals for subsequent use by
a digital computing device, such as a microprocessor, to control the
operation of a servomechanism. However, while effective for many
applications, synchros can generate analog synchro signals which are not
truly accurate representations of the status of a mechanical output
component. For instance, errors may be generated in the structure of the
synchro which can cause the analog synchro signals to vary in amplitude,
offset, and quadrature. Errors may also be introduced when the analog
synchro signals are processed by the other components in a servomechanism.
Consequently, these errors can reduce the accuracy of a status signal.
Synchro-to-digital converter chips and other electronic hardware may be
used to attempt to compensate for errors in the analog synchro signals.
However, such hardware may only be effective for correcting errors that
remain relatively constant over a period of time. These hardware devices
may not be effective for correcting errors that vary over time. In
addition, a relatively large number of these devices may be required in a
servomechanism since these devices may only have a limited number of
inputs and outputs. Consequently, these hardware devices may increase the
cost and reduce the reliability of the servomechanism.
It is known to use digital signal processing technology to compensate for
errors in the analog output signals from resolver components. Such
technology can compensate for errors that vary over time as well as errors
that remain relatively constant over a period of time. However, the
current state of known digital signal processing technology cannot
compensate for errors in the analog output signals from synchros.
In light of the shortcomings in the known art, there is a need to use
software-based digital signal processing technology to correct errors in
the synchro signals so that the status signal is truly representative of
the status of a mechanical output component. A need also exists to use
software-based digital signal processing technology to correct for
constant and time-varying errors in the synchro signals. Another need
exists to use software-based digital signal processing technology which
can accept a greater number synchro inputs as compared to the known art.
Similarly, a need exists for a generic card in the software-based digital
signal processing circuit which is adapted to accept a plurality of inputs
which are not limited to the specific inputs of a particular customer.
Preferred embodiments of the present invention accomplish some or all of
these objectives. The present invention relates to a method and apparatus
which utilizes a software-based digital signal processing circuit to
generate a signal which is representative of the status of a movable
component. A preferred embodiment of the software-based digital signal
processing circuit preferably improves the accuracy of a servomechanism. A
preferred embodiment of the software-based digital signal processing
circuit may also reduce the cost of the servomechanism by eliminating the
need for special synchro-to-digital converter chips or other
error-correcting hardware.
A preferred embodiment of the apparatus of the present invention includes a
synchro which is connected to a movable component. An analog reference
excitation may be generated, or a digital reference signal may be
generated and converted to an analog reference excitation by a
digital-to-analog converter or any other suitable device. The analog
reference excitation is applied to the synchro, and the synchro generates
analog synchro signals which bear a relationship to the status of the
movable component. The analog synchro signals are converted to digital
synchro signals by a plurality of analog-to-digital converters. If
necessary, the plurality of analog-to-digital converters may also convert
the analog reference excitation to a digital reference signal. The digital
synchro signals and the digital reference signal are provided to a
software-based digital signal processing circuit which preferably corrects
constant and time-varying errors in the digital synchro signals and
generates a status signal which is representative of the status of the
movable component. For instance, the status signal may represent the
angular position of the movable component. A different embodiment of the
status signal may represent the angular velocity of the movable component.
The software-based digital signal processing circuit may include a
microprocessor. The software-based digital signal processing circuit may
simultaneously accept multiple sets of synchro signals. In fact, a
preferred embodiment of the software-based digital signal processing
circuit may accept approximately 88 sets of synchro signals. Consequently,
a preferred embodiment of the software-based digital signal processing
circuit preferably eliminates the need for discrete synchro decoders for
each set of synchro signals.
In addition, a preferred embodiment of the software-based digital signal
processing circuit utilizes a software algorithm to correct for constant
and time-varying errors in the digital synchro signals. For instance, a
preferred embodiment of the software-based digital signal processing
circuit may factor out signal attenuation, insure quadrature, and/or
reduce phase shift variation of the digital synchro signals prior to
determining the status signal.
A generic card may be used in the software-based digital signal processing
circuit. The software algorithm may be stored on a card separate from the
generic card. The generic card is preferably adapted to accept a plurality
of inputs which are not limited to the specific inputs of a particular
customer. As a result, the same type of generic card may be used for
substantially all customers even though they may use different inputs,
thereby eliminating the need for a special card for each customer or each
type of inputs. With a preferred embodiment of the generic card, only the
software needs to be reconfigured to adapt the generic card to handle the
specific inputs of a particular customer. The software may be reconfigured
in the field by reprogramming a flash EPROM. The generic card preferably
does not have to be removed from the chassis or replaced in order to
reprogram the flash EPROM.
In addition to the novel features and advantages mentioned above, other
objects and advantages of the present invention will be readily apparent
from the following descriptions of the drawings and preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a symbolic diagram of a preferred embodiment of the synchro;
FIG. 2 is a flow diagram illustrating the steps that a preferred embodiment
of the software-based digital signal processing circuit takes in order to
determine the status signal; and
FIGS. 3 through 20 are schematic diagrams of a preferred embodiment of the
generic card of a software-based digital signal processing circuit.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)
The present invention is directed to a method and apparatus which uses a
software-based digital signal processing circuit to generate a status
signal which is representative of the status of a movable component. In
performing this function, a preferred embodiment of the present invention
eliminates the need for special synchro-to-digital converter chips and
error-correcting hardware. In addition, a preferred embodiment of the
present invention may improve the accuracy of a servomechanism by
correcting for constant and time-varying errors in the synchro signals.
FIG. 1 is a symbolic diagram of a preferred embodiment of a synchro. It is
well understood in the art that a synchro may be connected to a movable
component. For example, a synchro may be connected to a motor that
includes a stationary stator and an output shaft or rotor. The synchro
accepts an analog reference excitation R1, R2 at its rotor terminals, and
the synchro generates analog synchro signals S1, S2, S3 at its synchro
terminals. The analog synchro signals S1, S2, S3 are at the reference
frequency. It is well known in the art that the amplitude ratios of the
line-to-line voltages V.sub.1-2, V.sub.2-3, and V.sub.1-3 bear an explicit
mathematical relationship to the angular position of the movable component
relative to a reference position.
In a preferred method of the present invention, the analog reference
excitation is converted to a digital reference signal, and the analog
synchro signals are converted to digital synchro signals. A plurality of
analog-to-digital converters or any other suitable device or devices may
be used to digitize the signals. The digital reference signal and the
digital synchro signals are then provided to a software-based digital
signal processing circuit. The software-based digital signal processing
circuit uses the digital reference signal and the digital synchro signals
to determine a status signal that is representative of the status of the
movable component.
FIG. 2 is a flowchart illustrating the steps that a preferred embodiment of
the software-based digital signal processing circuit may take in order to
determine the status signal. In FIG. 2, digital synchro signals X, Y, and
Z and digital reference signal Ref are input to a software-based digital
signal processing circuit. It is preferred to filter the digital reference
signal and the digital synchro signals to reduce signal noise prior to
determining the status signal. In this embodiment, the software-based
digital signal processing circuit bandpass filters the digital reference
signal and the digital synchro signals.
Next, the software-based digital signal processing circuit preferably
searches for the peak of each signal. Depending on the sample rate, it may
not be possible to guarantee that a sample will fall exactly on the peak
of a signal. Therefore, it is preferred to find two samples for each
signal that encompass its peak amplitude. The digital reference signal REF
is preferably always at full amplitude. Therefore, the search is
preferably performed initially on the digital reference signal REF. The
software-based digital signal processing circuit may sample the digital
reference signal REF to determine two peak encompassing points of the
digital reference signal REF. For example, the software-based digital
signal processing circuit may scan the samples to find where the rate of
change between two samples changes signs. The software-based digital
signal processing circuit may then determine the sample time for the two
peak encompassing points of the digital reference signal REF.
The software-based digital signal processing circuit preferably uses the
sample time to retrieve two peak encompassing points from each of the
digital synchro signals. The software-based digital signal processing
circuit may use this information to determine the peak amplitudes of the
digital synchro signals. For example, the general signal equation is:
data=TruePeak.times.Sin[A]
For each digital synchro signal, there are two peak encompassing points
(for example, data0 and data1). This provides the following equations:
data0=TruePeak.times.Sin[A]
data1=TruePeak.times.Sin[A]+dA
where dA is a constant, known separation between the two data points, data0
and data1. This separation is based off the sample rate and is as follows:
##EQU1##
The above equations may be solved to determine the value of TruePeak. The
solution is:
##EQU2##
This equation may be used to determine the true peak amplitudes of digital
synchro signals X, Y, Z.
Any of the true peak amplitudes may be used to determine the synchro angle
as shown below:
TruePeak of digital synchro signal X=Sin[SynchroAngle]
TruePeak of digital synchro signal Y=Sin[SynchroAngle+120 degrees]
TruePeak of digital synchro signal Z=Sin[SynchroAngle+240 degrees]
However, this approach has the disadvantage of not being able to factor out
unaccounted signal attenuation such as losses due to the resistance in the
wiring. Therefore, it is preferred to use the two highest peak amplitudes
of the digital synchro signals to determine a status signal that is
representative of the status of the movable component. By using the two
highest peak amplitudes as determined above, unanticipated attenuation and
phase shifting of the digital synchro signals may be factored out.
Under this approach, there are six possible scenarios for determining the
synchro angle and the resulting status signal:
If TruePeak of X>TruePeak of Y>TruePeak of Z, then use TruePeak of X and
TruePeak of Y; (1)
If TruePeak of Y>TruePeak of X>TruePeak of Z, then use TruePeak of X and
TruePeak of Y; (2)
If TruePeak of X>TruePeak of Z>TruePeak of Y, then use TruePeak of X and
TruePeak of Z; (3)
If TruePeak of Z>TruePeak of X>TruePeak of Y, then use TruePeak of X and
TruePeak of Z; (4)
If TruePeak of Z>TruePeak of Y>TruePeak of X, then use TruePeak of Y and
TruePeak of Z; (5)
and
If TruePeak of Y>TruePeak of Z>TruePeak of X, then use TruePeak of Y and
TruePeak of Z (6)
For cases 1 and 2, the following formula may be used to determine the
synchro angle:
##EQU3##
For cases 3 and 4, the following formula may be used to determine the
synchro angle:
##EQU4##
For cases 5 and 6, the following formula may be used to determine the
synchro angle:
##EQU5##
The result of the above formulae generates an angle between 0 and 180
degrees. If the true synchro angle is above 180 degrees, it is preferred
to perform one more test. For cases 1, 2, 3, and 4, if the true peak of X
is less than zero, then 180 degrees may be added to the calculated angle
to obtain a true angle in the range of 0 to 360 degrees. For cases 5 and
6, if the true peak of Y is greater than zero, then 180 degrees may be
added to the calculated angle to obtain a true angle in the range of 0 to
360 degrees. As a result, the software-based digital signal processing
circuit is adapted to provide a true synchro angle in the range of 0 to
360 degrees which is representative of the status of the mechanical output
component. The software-based digital signal processing circuit may then
send a status signal to a display processor which allows the angular
position to be displayed on a display screen. Alternatively, additional
well-known calculations may be performed to determine a status signal
which represents the angular velocity of the movable component.
The present invention is also directed to an apparatus for generating a
status signal which is representative of the status of a movable
component. The movable component may be a rotatable shaft such as the
rotor of a motor. A preferred embodiment of the apparatus comprises a
synchro, a plurality of analog-to-digital converters, and a software-based
digital signal processing circuit. An analog reference excitation is
applied to the synchro, and the synchro is adapted to generate analog
synchro signals which bear a relationship to the status of the mechanical
output component. A plurality of analog-to-digital converters is in
electrical communication with the synchro. The analog-to-digital
converters are adapted to convert the analog synchro signals to digital
synchro signals. In addition, the plurality of analog-to-digital
converters may also be adapted to convert the analog reference excitation
to a digital reference signal. The software-based digital signal
processing circuit is in electrical communication with the plurality of
analog-to-digital converters. The software-based digital signal processing
circuit is preferably adapted to correct errors in the digital synchro
signals and to generate a status signal which is representative of the
status of the mechanical output component. The status signal may represent
the angular position of the mechanical output component. A different
embodiment of the status signal may represent the angular velocity of the
mechanical output component.
The software-based digital signal processing circuit may include a
microprocessor. The software-based digital signal processing circuit also
preferably includes a generic card. FIGS. 3 through 20 are schematic
diagrams of a preferred embodiment of the generic card. The generic card
is preferably adapted to accept a plurality of inputs which are not
limited to the specific inputs of a particular customer. In addition, the
generic card preferably outputs signals which are processed by the
software algorithm of the software-based digital signal processing
circuit.
The same generic card may be used for substantially all customers even
though they may have different inputs. With a preferred embodiment of the
generic card, only the software may need to be reconfigured to handle the
specific inputs of a particular customer. The software may be reconfigured
in the field by reprogramming a flash EPROM. It is preferred that the
generic card does not have to be replaced in order to reprogram the flash
EPROM.
The software algorithm of the software-based digital signal processing
circuit preferably corrects constant and time-varying errors in the
digital synchro signals. A preferred embodiment of the software-based
digital signal processing circuit factors out any amplitude variation of
any of the peak amplitudes of the digital synchro signals prior to
generating the status signal. The software-based digital signal processing
circuit may also reduce any phase shift variation of any of the digital
synchro signals prior to generating the status signal.
The present invention further includes a servomechanism comprising a motor,
a synchro, a plurality of analog-to-digital converters, and a
software-based digital signal processing circuit. The motor has a stator
and a rotor, and the rotor is driven to rotate about an axis relative to
the stator. The synchro is adapted to generate analog synchro signals
which bear a relationship to the status of the rotor. The plurality of
analog-to-digital converters is in electrical communication with the
synchro. The plurality of analog-to-digital converters is adapted to
convert the analog synchro signals to digital synchro signals. The
software-based digital signal processing circuit is in electrical
communication with the plurality of analog-to-digital converters. The
software-based digital signal processing circuit is adapted to correct
errors in the digital synchro signals and to generate a status signal
which is representative of the status of the rotor.
The preferred embodiments herein disclosed are not intended to be
exhaustive or to unnecessarily limit the scope of the invention. The
preferred embodiments were chosen and described in order to explain the
principles of the present invention so that others skilled in the art may
practice the invention. Having shown and described preferred embodiments
of the present invention, those skilled in the art will realize that many
variations and modifications may be made to affect the described
invention. Many of those variations and modifications will provide the
same result and fall within the spirit of the claimed invention. It is the
intention, therefore, to limit the invention only as indicated by the
scope of the claims.
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